Spot on with that Mr Pickles if the music is good why limit yourself with what you can play. I love my Rnb, Early Soul, Latin etc and would look to mix all these in when dj-ing. IMO a good dj will always mix it up, if you stick to one genre it all starts to sound very samey!
Why not mix in oldies with underplayed soul followed by some latin, Rnb and funky soul. I say get it all in the mix, it's what makes a quality dj from a average dj!